Pendant control for overhead crane



Dec. 15, 1970 R. J. MESSMER" 3,548,272

PENDANT CONTROL FOR OVERHEAD CRANE Filed May 24, 1967 2 Sheets-Sheet l1970 R. J. MESSMER PENDANT CONTROL FOR OVERHEAD CRANE 2 Sheets-Sheet 2Filed May 24, 1967 PENDANT CONTROL OTOR HOIST }MOTOR 3 PHASE POWERSUPPLY United States Patent US. Cl. 31817 19 Claims ABSTRACT OF THEDISCLOSURE A pendant control for an overhead bridging crane havingreversible trolley, bridge and hoist motors includes a pendant housing,an electrical cable attached to the housing, means movable along thecrane bridge for suspending the housing and counterbalancing its weight,and three drum switches on the housing coupled to the trolley, bridgeand hoist motors through the cable for controlling motor direction as afunction of the direction of switch rotation from a normal position andmotor speed as a function of the angle of rotation from normal position.Each switch has a control knob adapted to be grasped byone hand to pullthe housing to the load site and control direction and angle of switchrotation. Each switch also has resilient means to return it to thenormal position when released so that it is fail safe and has contactsspaced from insulation upon which tracking resulting from arcing at theswitch contacts could occur.

This invention relates to manually operated controls for travelingbridge cranes and in particular to pendant controls which permitoperation of the bridge, trolley and hoist motors of the crane from thefloor and control both direction and speed of such motors.

Overhead bridge cranes are conventionally controlled by a craneman whorides in a cab on the crane and manipulates electrical switches tocontrol movement of the crane in bridge, trolley and hoist directions tothe locations of the load where another workman on the ground, sometimesreferred to as the hookon, secures the crane hook to the load. The trendin recent years has been to eliminate the operator in the cab on thecrane and to control the crane from the ground by means of radio typecontrols or pendant controls having a plurality of pushbutton type,electrical switches for controlling direction and speed of the bridge,trolley and hoist motors. Radio type controls are prohibitivelyexpensive for factories having numerous cranes. Known pendant cranecontrols of the pushbutton type are bulky, cumbersome and diflicult tooperate; they are expensive and difficult to maintain; and they aredangerous in that they occasionally fail electrically and cause loss ofcontrol of the crane by the operator and result in a runaway crane.

Commercially available pendant crane controls usually have eight or morepushbutton switches mounted in a row in an elongated casing to permitthe operator to vary both direction and speed of the bridge, trolley andhoist motors. The difiiculty of locating the desired pushbutton requiresthe operator to take his eyes off the load and the hoisting block.Further, the large number of pushbuttons makes it difficult for theoperator to quickly acquire the familiarity needed for effectiveoperation of the control. The casings for such pendant controls areheavy and bulky and require the operator to use both hands to grasp thecontrol with suflicient force to pull the control to the site of theload. The weight and large size of the control often necessitatestilting the control so that the operator can see which pushbutton topress, and the continual tilting soon results in breakage of the wiresof the control cable. Commercially available pendant crane controlsutilize 3,548,272 Patented Dec. 15, 1970 spring loaded pushbuttonswitches which require such high actuating force that the operator mustsqueeze with thumb and fingers of both hands to operate the switch andhold it closed, and the operators fingers are soon fatigued from holdingthe pushbutton switch operated. The bulkiness of the pendant control,the difficulty of locating the desired pushbutton without taking theoperators eyes oflt' the load, and the difficulty of operating theswitches make it impracticable for the control operator to also hook onthe load.

The pushbutton switches of commercially available pendant controls areof the type wherein movable metallic contacts sequentially bridgebetween different pairs of stationary metallic contacts arranged aroundthe inner periphery of the insulating switch housing. Arcing betweenstationary and movable contacts of the pushbutton switches causesdeposition of carbon particles, or tracking, on the surface of theswitch insulating housing. Such tracking often causes sustained arcingbetween the switch contacts with consequent destruction of the switchhousing by the heat of the arc. Further, such arcing occasionallyresults in loss of control of the crane and a runaway condition which isa hazard to life and property.

It is an object of the invention to provide an improved pendant controlfor an overhead bridge crane which eliminates both the operator in thecab on the crane and the hookon on the floor and permits any worker onthe floor to easily control the crane and to hook on the load.

It is a further object of the invention to provide an improved pendantcontrol for an overhead bridge crane which a worker can easily grasp andpull with one hand to the load site and hook on the load with one handwhile controlling the crane with the other hand.

It is a further object of the invention to provide such a pendant cranecontrol having a minimum number of switch actuating means which must beactuated to control direction and speed of the hoist, bridge and trolleymotors and which actuating means can be selected by touch only, thuspermitting the operator to continually keep his eyes on the load as itis being hooked up and hoisted. Another object is to provide such apendant crane control having switch actuating means which require onlysmall force to operate with one hand and do not fatigue the operatorsfingers to hold the switch operated and which actuating means itself maybe grasped by the operator with one hand to pull the control to thevicinity of the load. Still another object is to provide such pendantcrane control which is considerably smaller, lighter and more ruggedthan prior art devices; which is easier and simpler to operate thanprior art devices; and which requires less maintenance and installationtime than prior art pendant crane controls. A still further object is toprovide such a pendant crane control which permits the operator toquickly acquire the familiarity required for effective operation.

A further object of the invention is to provide a fail safe pendantcrane control wherein the switch actuating means automatically restorethe switches to off position when they are released, thereby stoppingthe crane. Another objeot is to provide such a control which preventsloss of control and runaway condition of the crane as occurred withprior art apparatus. A still further object is to provide such a pandantcrane control wherein the contacts of the electrical switches whichcontrol direction and speed of the bridge, trolley and hoist motors arespaced a substantial distance from the switch insulation and sustainedarcing between switch contacts cannot result from deposition of carbonor tracking.

These and other objects and advantages of the invention will be morereadily apparent from the following detailed description when consideredin conjunction with the accompanying drawing wherein:

FIG. 1 is a front view of a typical overhead crane embodying theinvention;

FIG. 2 is an end view of the apparatus of FIG. 1;

FIG. 3 is a front view of the switch housing of the pendant control ofFIG. 1;

FIG. 4 is a side view of the device of FIG. 3 with a portion of asidewall removed to illustrate the switch construction;

FIGS. 5, 6 and 7 are views taken along lines VV, VIVI and VIIVII of FIG.4;

FIG. 8 is a schematic diagram of a portion of the electrical circuit forone of the motors, namely, the hoist motor of the crane of FIG. 1;

FIG. 9 is an enlarged view of the switch return, torsion spring meansshown in FIG. 4; and

FIG. 10 is an enlarged view of the portion of FIG. 4 showing the switchactuating means.

Referring to FIGS. 1 and 2, the invention is shown applied to a typicaloverhead bridging crane having a bridge 10 traveling along spaced apartparallel crane runways 11 (only one being shown). The crane bridge 10 isillustrated as an I-bearn, and the crane runways 11 are shown as I-beamssuspended from the ceiling 12 by depending rods 14. The crane bridge 10runs on the lower flanges of the I-beam runways 11 and each end thereofis rigidly affixed to an end truck having a pair of spaced apart endtruck channel members 16 extending parallel to and disposed on oppositesides of runway 11. Brackets 17 are affixed to the ends of the truckchannel members 16, and end truck wheels 18 rotatably mounted onbrackets 17 ride on the lower flanges of the I-beam runways 11. Thecrane bridge 10 is propelled along the crane runways 11 by tractionwheels 20 fastened to the crane end trucks and engaging the lowersurface of the I-beam runways 11. The traction wheels 20 are driven by abridge motor 21 mounted on the bridge 10 through means shown onlyschematically in the drawing.

Supported by and operating on I-beam bridge 10 is an electric hoistmechanism 23 propelled along the crane bridge by a trolley mechanismincluding a traction wheel 24 engaging the lower surface of I-beambridge 10 and driven by a trolley motor 26. Wheels 28 engaging the lowerflange of I-beam bridge 10 support the trolley mechanism through yokemembers 29. Hoist mechanism 23 includes a hoist hook block 31 raised orlowered by means of a hoist motor 32 through hoist chain 33 andsupported by wheels 28 engaging the lower flange of I-beam bridge 10.The trolley mechanism may be connected to the hoist mechanism by meansof a link 34.

The particular overhead crane disclosed does not constitute a novel partof the present invention and is only described to illustrate a typicalapparatus which the invention controls.

The bridge, trolley and hoist motors 22, 26 and 32, respectively, of thecrane are remotely controlled by a worker at ground level by means of apendant crane control box, or switch housing 36, connected to anelectrical control cable 37. Electrical connections from the controlcable 37 to the motors on the movable crane may be completed throughconventional power collector bars and power collector shoes which do notconstitute part of the invention and are omitted to shorten thedescription and facilitate the understanding of the invention.

Control box 36 and several loops of control cable 37 are preferablysupported for movement by the operator along bridge 10 by means ofwheels 40 engaging the lower flange of I-beam bridge 10. Control box 36is normally suspended in midair in a convenient position where it isreadily accessible to the worker and its weight and that of controlcable 37 are counterbalanced by a wire cable 41 depending from a cablerewinding reel 42 supported on a pair of the wheels 40 for movementalong bridge 10.

One end of wire cable 41 may be affixed to a rotatable drum 43 of cablerewinding reel 42 urged by a clock type spiral spring (not shown) toprovide an upward lifting force on cable 41 slightly greater than theweight of control box 36 and control cable 37 and to resiliently resistwithdrawal of cable 41 from reel 42 when control box 36 is pulleddownward by the operator to any desired position, such as that shown indotted lines in FIG. 1, and to retract wire cable 41 and raise controlbox 36 to its normal position when released by the operator. Wire cable41 may run through a pulley rotatably mounted on a pulley block 44 andbe affixed at its other end to rewinding reel 42, and pulley block 44may be connected to control box 36 by a stub piece of wire cable 46 andbe affixed to the electrical cable 37 at a point removed from controlbox 36 by suitable clamping means 45. Reel 42 retracts wire cable 41until pulley block 44 abuts against reel 42, and it will be appreciatedthat pulley block 44 thus acts as a stop to normally position controlbox 36 in a convenient horizontal plane.

Control box 36 is only approximately one-third the height and a minorfraction of the weight of commercially available pushbutton type pendantcrane controls, and it will be appreciated that no flexing of thecontrol cable 37 occurs as the control box 36 is lowered to convenientheight by the operator. The rewinding reel 42 counterbalances the weightof control box 36 and control cable 37 so that the operator may easilymove conrol box 36 up or down with one hand if required to bend over tohook in the load with his other hand.

As shown in FIGS. 3 and 4, control box 36 has three rotatable, doorknobshaped, switch actuating handles, or control knobs 50T, 50H and 50Bthereon which control both speed and direction of the trolley, hoist andbridge motors 22, 26 and 32, respectively. Each control knob 50 iseasily grasped by one hand of the operator to pull control box 36 to thesite of the load, and the reduction in the number of switch actuatingmeans to three, in comparison to the eight pushbuttons of commerciallyavailable pendant crane controls, permits the operator to easily selectthe desired switch actuating means by touch only and does notnecessitate tilting the control box and taking the operators eyes offthe hoist and the load as is required by pushbutton type pendantcontrols.

Control box 36 preferably comprise an elongated hollow casing 51 closedby a removable L-shaped cover 52 and secured thereto by machine screws.Both casing 51 and cover 52 may be castings of suitable light weightmetal such as aluminum. Stub cable 46 is afiixed to an eye 54 integralwith cover 52, and electrical control cable 37 may extend into theinterior of casing 51 through a threaded connector 55 on cover 52. Threespaced apart tubular projections 57 on cover 52 receive the reduceddiameter portions 53 of control knobs 50T, 50H and 50B. Each controlknob 50 has an axial bore which receives the shaft portion 60 of acoupling member 61 and is rigidly affixed thereto by a set screw 62which is threaded into the shaft portion 60. The tubular projections 57are counterbored from the inner surface thereof to provide shoulders 64against which enlarged diameter portions 65 of the coupling members 61abut to prevent movement in an axially outward direction. The couplingmembers 61 are positioned within leeve bearings 67 disposed within thecounter-bored portions of the tubular projections 57, and each couplingmember 61 has an axial bore which receives the operating shaft 68 of anelectrical drum switch, or controller 70 and is affixed to shaft 68 by aradially extending roll pin 71.

The three drum switches 70 complete energizing circuits to contactors orrelays described hereinafter which open and close circuits forcontrolling speed and direction of the bridge,trolley and hoist motors22, 26 and 32. The three drum switches 70 are identical and only onewill be described. Drum switch 70 has a U-shaped mounting frame 73, oneleg of which is afiixed to the inner surface of cover 52 by screws 74.The portion of switch operating shaft 68 disposed between the legs ofU-shaped mounting frame 73 is of square cross section, an insulatingtube 76 of square cross section (see FIGS. -8) surroundsthis portion ofshaft 68, and a cylindrical metallic cam, or drum 77, having an axialbore of square cross section fits over insulating tube 76 and iselectrically isolated from the mounting frame 73 by insulating tube 76.Drum 77 has three sets of radially extending movable contact portions A,B and C at axially spaced positions adapted when operating shaft 68 isrotated to sequentially engage contact buttons 81 on upstanding metallicstationary contact fingers 108-113. Drum switch 70 has three sets, orpairs, of stationary contact fingers 108113 with the fingers of eachpair disposed on opposite sides of drum 77 in radial alignment with thecorresponding movable contact portions A, B or C on drum 77. The threeaxially spaced stationary contact spring fingers on each side of drum77, for example fingers 109, 111 and 113, are mounted by metallic screws83 on an elongated insulating strip 84 supported between the upstandinglegs of the mounting frame 73, and the screws 83 constitute terminalsfor connection of electrical leads. Thin insulating disks 86 surroundswitch operating shaft 68 at both ends of drum 77. A dog 87 having anaxial opening of square cross section fits over and rotates with thesquare cross section portion of switch operating shaft 68. A helicaltorsion switch return spring 88 surrounding switch operating shaft 68has a pair of arcuately spaced radially extending cars 90 at the ends ofthe spring which are disposed on opposite sides of an axially extendingarm 91 on dog 87 and also on opposite sides of an axially extending stoppin 93 afiixed to an upstanding leg of U- shaped mounting frame 73.

Manual turning of control knob 50 by the operator results in rotation ofswitch operating shaft 68 and dog 87 afiixed thereto, thereby displacingone radially extending car 90 on torsion spring 88 While the other endis prevented from movement by stop pin 93 and resulting in loading oftorsion spring 88. Switch actuating control knob 50 is thus resilientlyurged by torsion spring 88 towards its normal position when it isrotated in either the clockwise or counterclockwise direction from thenormal position. It will thus be appreciated that the disclosed controlis fail safe in that the switch control knobs 50B, 50T and 50H forcontrolling the bridge, trolley and hoist motors are always restored totheir normal position when released by the operator. Further, it will beappreciated that all arcing between movable and stationary switchcontacts occurs in air and is spaced a substantial distance from anyenclosing insulation members, thereby avoiding the tracking ofinsulation which caused the runaway condition in prior art cranecontrols of the pushbutton type.

Tubular projections 57 on cover 52 have radially extending surfaces 95which interfere with radial arms 96 or control knobs 50 to limitmovement of the control knobs in both directions of rotation.

The electrical circuits completed by the drum switch controllers 70actuated by the bridge, trolley and hoist control knobs 50B, 50T and 50Hare substantially identical and only the schematic circuits completed byhoist control knob 50H will be described. Such electrical circuits areschematically shown in FIG. 8 which omits the power collector bars andpower collector shoes used to complete energizing circuits to the motorson the crane and also omits the start and stop circuits which may becontrolled by START and STOP pushbutton switches on control box 36.Hoist motor 32 is shown as being of the three phase slip ring typehaving a rotor with phase windings 98 and a stator 99. Rotation of hoistmotor 32 in the forward direction to raise the load on hook block 31 isaccomplished by energizing the forward winding F of a reversing magneticmotor starter 100 to close movable contacts F1, F2 and F3 and completean energizing circuit from a three phase power supply line 101 to stator99 of hoist motor 32. Rotation of hoist motor 32 in the reversedirection to lower the load on hook block 31 is effected by energizingthe reverse winding R of reversing motor starter 100 to close itsmovable contacts R1, R2 and R3 and complete an energizing circuit frompower supply line 101 to stator 32 over conductors 103 in which two ofthe phases are reversed.

The phase windings 98 of the rotor are brought out through slip rings(not shown) to the serial arrangement of resistors R8, R9, R10 and R11in each phase connected to a common point such as ground to reduce thespeed of rotation of the hoist motor 32. The speed of hoist motor 32illustrated in FIG. 8 may be increased in three steps. Operation ofspeed control relay SCI closes its movable contacts SC1M and shorts theresistances R11 in the three phases. Similarly, operation of speedcontrol relays S02 and SC3 in sequence short circuits the resistancesR10 and R9 and increases the speed of hoist motor 32 in second and thirdsteps to increase the rate at which the load is raised or lowered.

Electrical power for energizing windings F and R of reversing motorstarter 100 and for energizing the operating coils of relays SCI, S02and SC3 may be derived from the secondary winding 105 of a transformer106 having its primary winding connected to a suitable source ofalternating current power. One side of transformer secondary winding 105is connected over a conductor 107 to stationary contact finger 108 whichmaintains continuous wiping engagement with raised cam portion A (seeFIGS. 5 and 8) extending around approximately 220 degrees of metallicdrum 77 of controller 70. The opposite side of transformer secondaryWinding 105 is connected through conductor 110 to one side of each ofthe forward and reverse windings F and R of motor starter 100 and alsoto one side of the operating coils of each of the speed control relaysSCI and SCZ and SC3.

Rotation of hoist control knob 50H in clockwise direction, as seen fromthe front of control box 36, brings raised cam portion A on drum 77 intoengagement with finger contact 109 disposed on the opposite side of drum77 from finger centact 108 and completes an energizing circuit through aconductor connected to finger 109 to forward winding F of motor starter100, thereby closing contacts F1, F2 and F3 and causing hoist motor 32to run in the forward direction at its lowest speed. Further rotation ofhoist control knob 50H in the clockwise direction brings a raised camportion B1 extending approximately 110 degrees around metallic drum 77into engagement with control finger 110 disposed adjacent contact finger108 to complete an energizing circuit over a conductor 116 connected tofinger 110 to the operating winding of speed control relay SCI, therebyclosing its contacts SCIM and shorting out resistances R11 to increasethe speed of hoist motor 32. It will be appreciated that cam portion Aremains in wiping contact with stationary contact finger 108 to keepforward winding F energized while the speed of motor 32 is beingchanged. Further rotation of hoist control knob 50H in the clockwisedirection brings a raised cam portion C1 extending over approximately 70degrees of metallic drum 77 into engagement with stationary contactfinger 112 disposed adjacent finger 110 to complete an energizingcircuit over a conductor 117 connected to finger 112 to the operatingcoil of relay SC2, thereby causing it to operate its contacts and Shortout resistances R10 and thus increase the speed of hoist motor 32 inanother step. Still further rotation of hoist control knob 50 in theclockwise direction brings a raised cam portion C2 extending overapproximately 66 degrees of drum 77 into engagement with a stationarycontact finger 113 disposed opposite finger 112 to complete anenergizing circuit over conductor 118 connected to finger 113 to theoperating coil of speed control relay SC3, thereby operating itscontacts to short out resistances R9 and increase the speed of hoistmotor 32 in another step. When the operator releases control knob 50H,loaded torsion spring 88 acting on arm 91 of dog 87 rotates the switchshaft 68 to restore the controller 70 to its normal position, therebyopening the circuits to forward winding F and speed control windingsSCI, SC2 and SC3 and stopping motor 32.

Manual operation of hoist control knob 50H in the counterclockwisedirection brings a raised cam portion B1 (see FIGS. 6 and 8) extendingacross approximately 110 degrees of metallic drum 77 into engagementwith stationary contact finger 111 disposed between contact fingers 109and 113 to complete an energizing circuit over a conductor 119 connectedto finger 111 to the reverse winding R of motor starter 100, therebyclosing contacts R1, R2 and R3 and causing hoist motor 32 to run in thedirection to lower the load on hook 31. Further rotation of control knob50H in the counterclockwise direction sequentially brings cam portionsB2, C2 and C1 into engagement with contact fingers 110, 112 and 113,respectively, to complete energizing circuits to the operating windingsof speed control relays SCI, SC2 and SC3 in sequence as control knob 50His rotated further in the counterclockwise direction and thus controlthe speed of hoist motor 32 in three steps.

Portions of conductors 107 and 115-119 are shown in dotted lines toindicate that they are in control cable 37.

Control box 36 is light in weight and only approximately one-third theheight of commercially available pushbutton type devices, and furtherits weight is counterbalanced by cable rewind reel 42. Switch controlknobs 50 are easy to grasp by the operator with one hand to pull thecontrol box 36 to the site of the load. Only three switch actuatingknobs 50 are required to control both speed and direction of the cranebridge, trolley and hoist motors in comparison to six pushbuttons forthe same purpose on commercially available pushbutton pendant cranecontrols, thereby permitting the operator to easily select the desiredswitch actuating means by touch only and operate it with one hand whilepermitting him to hook on the load with his other hand to keep his eyeson the load and hoist block at all times. The drum 77 and fingercontacts are spaced a substantial distance from insulation so thatdeposition of carbon and tracking cannot occur which frequently causessustained arcing in pushbutton switches of known pendant crane controls,and it will be appreciated that this feature prevents loss of control ofthe crane by the operator, eliminates the hazard of runaway cranes, andminimizes maintenance problems in comparison to pushbutton type pendantcrane controls.

While only ,a single embodiment of the invention has been illustratedand described, many modifications and variations thereof will be readilyapparent to those skilled in the art, and consequently it is intended tocover in the appended claims all such modifications and variations whichare within the true spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows: I

1. In combination with a bridging crane having reversible trolley,bridge and hoist motors for moving the bridge and hoist of said crane introlley, bridge and hoist directions,

a pendant switch housing,

means movable along the bridge of said crane for suspending said housingfrom said crane,

an electrical cable attached to said housing,

three rotatable switch means on said housing each of which is associatedwith a respective one of said motors and coupled thereto through saidcable for controlling the direction and speed of said one motor asfunctions of the direction and angle of rotation of said switch meansfrom a normal position, and

three rotatable switch actuating handles on said housing each of whichis operatively connected to one of said switch means and adapted to begrasped by one hand of the crane operator to pull said housing to theload site and being rotatable by one hand to control direction and angleof rotation of said switch means.

2. In the combination defined by claim 1 wherein each switch means is adrum switch having a rotatable operating shaft and said switch actuatinghandle in a control knob operatively connected to said shaft.

3. In the combination defined by claim 2 wherein each drum switchincludes a rotatable metallic drum and a plurality of stationary contactfingers disposed adjacent said drum and wherein said drum has aplurality of radially projecting portions adapted to sequentially engageand make wiping electrical contact with said fingers when said drum isrotated by said control knob.

4. In the combination defined by claim 3 wherein each drum switchincludes a plurality of pairs of contact fingers spaced apart axially ofsaid drum and the fingers of each pair are disposed on opposite sides ofsaid drum and said radially projecting portions on said drum are inradial alignment with said sets of fingers.

5. In the combination defined by claim 3 wherein one of said contactfingers is electrically connected to one side of a source of electricalpower and is in continuous engagement with said drum and the engagingportions of said radially projecting portions and said contact fingersbetween which arcing may occur are spaced an appreciable distance frominsulating members upon which tracking could result from said arcing.

6. In the combination defined by claim 1 and including resilient meansfor returning each said switch means and its actuating handle to saidnormal position when released by the operator.

7. In the combination defined by claim 1 wherein said bridge is a I-beamand said means for suspending said housing has a lifting componentslightly greater than the weight of said housing and said cable andincludes support wheels movable along the lower flange of said I-beambridge and stop means for normally holding said switch housing in apredetermined horizontal plane.

8. In the combination defined by claim 7 wherein said means forsuspending said housing includes a rewind reel supported from saidwheels, an elongated flexible member afiixed at its lower end to saidswitch housing and its upper end to said rewind reel, and wherein saidreel has resilient means for pulling upward on said flexible member witha force slightly greater than the weight of said housing and said cableand said stop means is secured to said flexible member.

9. In the combination defined by claim 3 wherein first and second ofsaid stationary contact fingers are first engaged by said radiallyprojecting portions of said drum when said drum switch is rotated in theclockwise and counterclockwise directions respectively from said normalposition and wherein said crane has associated with each motorelectromagnetic switching means having forward and reverse windings forcompleting electrical circuits to rotate said motor in forward andreverse directions when said forward and reverse windings respectivelyare energized and wherein said first and second contact fingers areelectrically connected to said forward and reverse winding through saidcable.

10. In the combination defined by claim 9 and including a plurality ofelectromagnetic relay means associated with each said motor for varyingthe speed of said motor and wherein a plurality of said contact fingersof the drum switch asociated with said motor are connected to theoperating coils of said relay means through said cable and said radiallyextending projections on said drum sequentially engage said plurality ofcontact fingers when said drum switch is operated in a first directionfrom a normal position and also engage said same plurality of contactfingers in the same sequence when said drum switch is operated in theopposite direction from said normal position.

11. In combination with a bridging crane having reversible trolley,bridge and hoist motors for moving the bridge and hoist of said crane introlley, bridge and hoist directions, electromagnetic switch meansassociated with each motor having forward and reverse windings forcontrolling the direction of motor rotation and being adapted tocomplete electrical circuits to operate said motor in forward andreverse directions when said forward and reverse windings are energized,and electrically operated means asociated with each motor for changingmotor speed;

a switch housing,

means movable along the bridge of said crane for suspending said switchhousing from said crane, an electrical cable attached at one end to saidhousing, three rotatable switch means in said housing each of which isassociated with a respective one of said motors and coupled theretothrough said cable for completing electrical energizing circuits to saidforward and reverse windings respectively'when rotated in oppositedirections from a normal position and for completing an electricalenergizing circuit to said speed changing means when rotated through apredetermined angle in either clockwise or counterclockwise directionsfrom said normal position, and

three rotatable switch actuating handles on said housing each of whichis operatively connected to one of said rotatable switch means andadapted to be grasped and rotated with one hand.

12. In the combination defined by claim 11 wherein said speed changingmeans varies motor speed in a plurality of steps and has a plurality ofoperating windings and changes motor speed one step when each saidoperating winding is energized and wherein said rotatable switch meansassociated with said motor completes electrical energizing circuitssequentially to said operating windings when rotated in both theclockwise and the counterclockwise directions from said normal position.

13. In combintaion with a bridging crane having reversible trolley,bridge and hoist motors for moving the bridge and hoist of said crane introlley, bridge and hoist directions, electromagnetic switch meansassociated with each motor having forward and reverse windings forcompleting electrical circuits to operate the motor in forward andreverse directions when said forward and reverse windings are energized,and means for changing the speed of said motor in a plurality of steps,said speed changing means having a plurality of operating windings andbeing adapted to vary motor speed one step when each operating windingis energized,

a pendant switch housing,

means movable along the bridge of said crane for suspending said switchhousing from said crane,

an electrical cable attached to said housing,

three rotatable drum switch means on said housing each of which isassociated with a respective one of said motors and coupled to saidforward and reverse and operating windings through said cable forcompleting electrical energizing circuits to said forward and reversewindings when rotated in clockwise and 10 trical energizing circuits tosaid operating windings when rotated in either the clockwise orcounterclockwise directions from said normal position, and threerotatable switch actuating control knobs on said switch housing each ofwhich is operatively connected to one of said drum switch means andadapted to be grasped and rotated with one hand to operate said drumswitch means and to pull said .housing along said bridge to the site ofthe load.

14. In the combination defined by claim 13 wherein each drum switchmeans has resilient means for returning it to said normal position whensaid control knob is released.

15. In the combination defined by claim 14 wherein said bridge is anI-beam and said means for suspending said housing includes wheelsmovable along the lower flange of said I-beam, a depending elongatedflexible member aflixed at its lower end to said housing, means havingan upward lifting component slightly greater than the weight of saidhousing and said cable supported from said wheels and secured to theupper end of said flexible member, and stop means on said flexiblemember for normally positioning said housing in a predeterminedhorizontal plane.

16. In the combination defined by claim 13 wherein said electromagneticswitch means is a reversible motor starter having forward and reversewindings and said drum switch means completes energizing circuits tosaid forward and reverse windings when rotated in opposite directionsfrom said normal position.

17. In the combination defined by claim 15 wherein said speed changingmeans includes a plurality of electrical relay means for changing thespeed of said motor and said drum switch means sequentially completesenergizing circuits to the operating coils of said relay means whenrotated in both the clockwise and in the counterclockwise directionsfrom said normal position.

18. In the combination defined by claim 17 wherein said drum switchmeans includes a rotatable metallic drum and a plurality of stationarycontact fingers disposed adjacent said drum and wherein said drum has aplurality of radial projections adapted to sequentially engage saidcontact fingers when said drum is rotated.

19. In the combination defined by claim 18 wherein one of said fingersis in continuous engagement with said drum and including a source ofelectrical power one side of which is connected to said one finger andthe other side of which is connected through said cable to one side ofsaid forward and reverse windings and to one side of said operating coilof each of said relay means.

References Cited UNITED STATES PATENTS 611,089 9/1898 Zweigbergk 3 l8952,794,103 5/1957 Moore 2006BIX 3,039,029 6/1962 Spafford 212-21X3,166,697 1/1965 Horsley 318-17 3,310,642 3/ 1967 Zeller 2006BIX3,346,705 10/1967 Slinkard 242-107X ORIS L. RADER, Primary Examiner US.Cl. X.R.

